Deposition of Polycyclic Aromatic Hydrocarbons (PAHs) into Northern Ontario Lake Sediments

Polycyclic aromatic hydrocarbons (PAHs) are priority pollutants that are produced through incomplete combustion of modern biomass and fossil fuels. In aquatic systems PAHs are absorbed by suspended matter and ultimately deposited into sediments. PAH fluxes to sediments have been declining in North American since the mid 1960s. Improving technology and regulations were expected to contribute to declining PAH concentrations; however, in some urban sediment there are recent increases in deposition. Trends in concentrations of pyrogenic PAHs and perylene were determined in the sediment of two lakes, in central Ontario. Intact piston cores that preserve the depositional history were collected from each site, sliced into 1 cm intervals and analyzed using gas-chromatography/ mass-spectrometry. Pyrogenic PAH trends at each site displayed unique characteristics suggesting differing extents of influence from various atmospheric sources. The upper core profile (above 8.5 cm) in the more remote site had decreasing PAH concentrations consistent with observations from Siskitwit Lake. The more urban site (above 3.5 cm) had increasing PAH concentrations suggesting modern anthropogenic activities have a larger influence in this region. Perylene fluxes at both sites do not correlate with the observed PAH fluxes, increasing in concentration with depth, thus indicating separate sources for this PAH, likely diagenesis within the sediments. Both sites had PAH concentrations exceeding the interim sediment quality guidelines in the uppermost sediment deposits. This study provides insights into the differential atmospheric deposition in Ontario and may aid in establishing strategies for reducing or mitigating the production of PAHs.